i on the other hand have a very good experiences, with c&v.
other than the excessive waiting hours on end, even sometimes not being able to get my car tuned,
but in the end, over approx a 3 year period i never had to change spark plugs,
my car has never ever pingend,
i made more power on low boost than expected, also with lazy timing and no cam gear timing.
they did exactly what i wanted.
all in all i guess it comes to who u personally trust